Well perforating apparatus



March 14, 1961 Filed Dec. 51, 1957 N m mw MW w}. v E w e United States v Patent WELL PERFORATING APPARATUS Robert J. Goodwin, Oakmont, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Dec. 31, 1957, Ser. No. 706,498

8 Claims. (Cl. 16655.5)

The present invention relates to new and useful improvements in apparatus for perforating and/or deforming oil Well casing, and more particularly pertains to such apparatus wherein the casing perforating or deforming units are hydraulically actuated both into and out of engagement with the casing by hydraulic pressure produced upon the burning of powder charges.

Broadly, the apparatus of the invention comprises a 2,974,727 .Patented Mar. 14,1951

entire series can be lowered within a borehole by means of a cable secured to the uppermost head. The cable supporting the series of heads can be of composite character including electrical conduits, whereby the powder charges can be selectively ignited from a surface position. The invention will be best understood upon reference to the accompanying drawings illustrative of a preferred embodiment, wherein:

Figure 1 is a broken elevational view of the perforating or deforming apparatus, with the driving and retracting heads being shown in vertical section; and

Figure 2 is an enlarged, horizontal sectional view of one of the working heads, such view being taken upon the plane of the section line 2-2 in Figure 1.

Referring to Figure 1, the numerals 10 and 12 designate generally a driving head and a retracting head,

respectively. The numerals 14 and 16 designate generally working heads disposed between .the driving and retracting heads 10 and 12. Each of the heads 10, 12, 14,

and 16 is provided with means. for detachably securing v the same to the head or heads immediately adjacent thereto. In the preferred construction, such means takes the 10, have a pair of spaced upstanding and inturned ribs,

vided to actuate the double-acting piston to retract a i work engaging member within the working head.

Each of the latter-mentioned means comprises a head having a cylindrical chamber therein in which a free floating piston is mounted for reciprocation. The lattermentioned chamber is adapted to contain a powder charge adjacent one end thereof and an electrical igniter therefor, with conduit means establishing communication between the other end of the chamber and one end of the chamber in the working head. The conduit means provided for one of the powder-charge containing heads communicates with a chamber in the working head on one side of the double-acting piston, while the conduit means,

provided for the other of the powder-charge containing heads communicates with the chamber of the working,

head on the other side of the double-acting piston.

The arrangement is such that with a hydraulic medium filling the working head, the conduit means and the portions of the chambers in the powder-charge containing heads on the sides of the free floating pistons adjacent the conduit means, ignition of one of the powder charges will act upon the hydraulic medium through the agency of the hydraulic floating piston to actuate the doubleacting piston of the working head in one direction, ,with subsequent ignition of the other powder charge causing a hydraulic action upon the double-acting piston to return it to its initial position.

Other important features of apparatus according to the invention reside in the provision of a vertical stack of working heads with two powder-charge containing heads which are disposed respectively above and below the stack of working heads. Each of the heads in such arrangement is detachably secured to the heads immediately adjacent thereto, with the conduit means being so arranged that ignition of the powder charge in one of the actuating heads drives all of the work engaging members to their positions projecting from their respective working heads, with the reverse being true upon ignition of the powder charge of the other actuating head. The

heads are all dimensioned so that when they are suspended as a vertical series from the uppermost of the heads, the

insulated electrical conductors, not shown.

such as ribs 19 shown in connection with head 14. Thus, heads 10 and 14 are detachably secured by means of the enlarged portion of the rib 18 being received between the ribs 19 at a position below the inturned portions of the ribs 19 and provided with proper clearance to assure a flexible attachment, it being understood that the headslll and 14 can be detached by removing a pin bolt 20 that extends through the ribs 18 and 19 and moving the head 14 relative to'the head 10 in a direction perdescribed in detail, it will be appreciated that each head is secured in like fashion to the heads adjacent thereto. Considering now the structure of the driving head 10,- 11; will be seen that the same comprises a housing 21 having a closed cylindrical chamber 22 therein. The

upper end of the housing 21 is provided with a threaded opening 23 in which a plug 24 is threadingly and removably received. The plug 24 closes the opening 23 and to insure such closure being pressure tight, the lower end of the plug 24 bears against an O-ring seal 26 that is seated against a shouldered portion of the opening 23, as shown. The plug 24 is provided with an opening 23 the'rethrough in which are seated a pair of blowout discs 30 which yield upon the pressure within the chamber 21 reaching a value described subsequently. An

electric cable 32 is sealed through the plug 24 and the same is of such character as to include a pair of A conventional replaceable electric igniter 34 is secured to the end of the cable 32 within the chamber 22 in appropriate contact within the conductors of the cable 32'. The igniter 34 can conveniently be of a type used in perforating equipment such as shown in U.S. Patent No. 2,381,929 (Item 119, Figure 12 of such patent).

A floating piston 36 is fitted within the chamber 22. for vertical reciprocation, such floating piston 36 including peripheral rings or packing 38' for preventing leakage past the floating piston 36. The plug 24 is removable as mentioned'previously, whereby a powder charge 40 can be placed in the chamber 22 above the floating piston 36, as shown, and igniter 34 secured in; position or replaced. The powder charge can be a slow burning, large gas volume yield type powder such as or Hercules.

The working heads 14 and 16 are essentially similar in character, and a detailed description of one will sufiice for both. The working head 14 is best shown in Figure 2 wherein it will be seen that the same comprises a housing 42 having a horizontal cylindrical opening 44 therethrough. A cylinder head 46 is threadingly fitted into one end of the housing 42 so as to close one end of the opening 44, a sealing ring 48 being provided for preventing leakage between the cylinder head 46 and the housing 42, as shown. The cylinder head has an outer surface that is convexed, as shown at 50, for a purpose presently to be described. The convex portion 50 of the cylinder head 46 may be provided with a groove or slot 52 for receiving a tool whereby the cylinder head 46 can be removed or replaced, as will be apparent.

A gland 54 is threadingly received in the housing 42 at the end of the opening 44 opposite the cylinder head 46, a sealing ring 56 being provided for establishing a tight seal between the gland 54 and the housing 42. The gland 54 is preferably provided with slots or grooves, such as the one shown at 58, whereby a tool can be readily applied to remove or replace the gland 54 in the housing 42.

A double-acting piston 60 is fitted in the opening 44 for reciprocation within the chamber 62 defined by the open-,

ing 44, the cylinder head 46 and the gland 54. If desired or deemed expedient, the piston 60 can be provided with packing or rings such as that shown at 38 for piston 36 in Figure 1. The piston 60 is provided with a cylindrical projection 64 on the side thereof adjacent the gland 54. A work engaging member 66 having a cylindrical outer surface that constitutes an extension of the projection 64 is deachably secured to the latter by means of a reduced threaded portion 68 of the work engaging member 66 being threadingly received within a threaded recess 70 at the outer end of the projection 64, as shown. As thus far described, it will be clear that introduction of a hydraulic medium into the chamber 62 intermediate the cylinder head 46 and the piston '60 at a pressure greater than that existing in the chamber 62 intermediate the piston 60 and the gland 54 will cause the piston 60 to move to the right, as shown in Figure 2, so that the work engaging member 66 will move from the illustrated retracted position within the housing 42 to a position projecting from the housing 42. On the other hand, whenever a hydraulic medium is introduced into the chamber 62 intermediate the piston 60 and the gland 54 at a greater pressure than that prevailing within the chamber 62 intermediate the piston 60, and the cylinder head 46, the piston 60 will move to the left, as shown in Figure 2, so that the work engaging member 66 will move from a position projecting from the housing 42' to the retracted position shown in Figure 2. The manner whereby a hydraulic medium under pressure is selectively introduced into the chamber 62 in either of the two described ways will be explained more fully hereinafter.

The retracting head 12 is quite similar to the pre viously described driving head 10, the same comprising a housing 69 having a closed cylindrical chamber 71 therein. The lower end of the housing 69 is provided with a threaded opening 72 in which a plug 74 is threadingly and removably received. The plug 74 closes the opening 72 and to insure such closure being pressure tight, the upper end of the plug 74 bears against an O-ring seal 76 that is seated against a shouldered portion of the opening 72, as shown. The plug 74 is provided with an opening 78 in which are seated a pair of blowout discs 80 which yield upon the pressure within the chamber 71 reaching arpredetermined value or becoming excessively high. An electric cable 82 is sealed through the plug 74, the same including a pair of insulated electrical conductors, not shown. An igniter 84, such as the previously described igniter 34, is replaceably secured 4, to the cable 82 within the chamber 71. A floating piston 86 is mounted within the chamber 71 for vertical reciprocation, and like piston '36 is provided with a pcripheral sealing ring 88 to prevent leakage thereby. A powder charge 90 of lesser quantity but of similar character to the powder charge 40 is contained within the chamber 71 below the piston 86, as shown. The removability of the plug '74 facilitates placement of the powder charge 90 and replacement of the igniter 84.

A system of conduits and passageways in the working heads 14 and 16 is provided whereby pressure generated within the head upon combustion of the powder charge 40 can be communicated to the working heads 14 and 16 in such a manner as to cause the work engaging member 66 of each of the working heads 14 and 16 to be forcibly projected from the working heads. Such system of conduits and passageways comprises a vertical passageway 92 through the housing 42 of the working head 14 (see Figure 2), which passageway 92 is provided with a lateral branch 94 that opens into the chamber 62 at a position closely adjacent the cylinder head 46, Although not shown, it will be understood that the working head 16 is provided with a similar passageway having communication with the chamber therein closely adjacent the cylinder head thereof. The driving head 10 is provided with a port 96 in which a conduit 98 is fixed. A conduit 100 is fixed to the upperside of the housing 42 of the working head 14 in communication with the passageway 92, with the adjacent ends of the conduits 98 and 100 being detachably coupled such as by the union coupling shown at 102. Although the conduits 98 and 100 are shown in Figure 1 as being in vertical alignment as is preferred, it will be appreciated that such arrangement is not essential, as the conduits can be flexible, as in conventional high-pressure hydraulic systems. The use of the coupling 102 is preferred, although the same can be dispensed with in such arrangements where the heads 10 and 14 are not to be uncoupled. A further conduit 104 is secured to the lower end of the working head 14 in communication with the passageway 92, and a similar conduit 106 is secured to the upper end of the passageway in the head 16 that corresponds to the passageway 92 in the head 14, with the adjacent ends of the conduits 104 and 106 being detachably coupled, as indicated at 108. As mentioned in connection with the conduits 98 and 100, the conduits 104 and 106 can also be of flexible character, such construction being especially preferred Where the corresponding passageways in the heads are not in vertical alignment. A conduit 110 corresponding to the conduit 104 is secured to the lowerside of working head 16 in communication with the conduit 106 by way of the passageway in the head 16 that corresponds to the passageway 92 in working head 14. The lower end of the. conduit 110 is closed by a cap 112.

From the foregoing, it will be appreciated that when the portion of the chamber 22 of the driving head 10 below the piston 36, as well as the passageway 92 in the head 14 and its counterpart in head 16, and the conduits 98, 100, 104, 106, and 110 are filled with a suitable hydraulic working fluid, preferably a high-boiling point, low-viscosity silicone oil, ignition of the powder charge 40 will cause the piston 36 to move downwardly, thereby exerting pressure upon the hydraulic working medium that is communicated into the working heads 14 and 16 so as to urge the pistons therein in such a manner as to cause the work engaging members of the working heads to be forcibly projected outwardly.

The blowout discs 30 are designed to yield at a pressure greater than that normally required to shoulder all the working pistons 60 against the glands 54, but less than that which would otherwise be built up by the powder charge 40. Therefore, the pressure generated by the charge 40 actuates all the pistons 60 and is then released by the yielding of the discs 30.

. 5 An analogous system ofvconduits and passageways to that just described is provided for causing pressure generated within the retracting head 14 to be communicated to the pistons of the working heads 14 and 16 so as to cause the work engaging members of the working heads to be retracted into positions such as that shown for work engaging member 66 in Figure 2. This analogous system of passageways and conduits comprises passageways in the heads 14 and 16 that communicate with the chambers therein at positions closely adjacent the glands of such working heads; such passageway for the working head 14 and its lateral communication with the chamber 62 adjacent the gland 54 being indicated at 114. A conduit 116 is fixed to the driving head 14 so as to communicate with the upper end of the passageway 114, and the upper end of the conduit 116 is closed by a cap 118. Communication between the lower end passponds to the passageway 114 in the head 14 has communication with the chamber 71 of the retracting head 12 by way of a conduit 126 fixed in a port 128 in the head 12, a conduit 130 fixed to the head 16 and a coupling 132 detachably securing the conduits 126 and 130. It will be appreciated that the conduits 126 and 130 can also be flexible.

Prior to ignition of the charge 90, the portion of the chamber 71 above the piston 86 is filled with a suitable hydraulic working medium such as a high-boiling point,

low-viscosity silicone oil, and the portions of the.work-' ing heads and associated conduits in communication with the chamber 71 are filled with a gas such as air, which is compressed during movement of the piston 60. There-' fore, subsequent ignition of the powder charge 90 through energization of the igniter 84 causes the floating piston 86 to move upwardly and cause such movement of the hydraulic working fluid (oil and air) as to act on the pistons of the working heads 14 and 16 in such a manner as to 'cause retraction of the work engaging members of the working heads.

The blowout discs 80 are designed to yield at a pressurevthat is greater than that required to drive the working piston 60 to its retracted position and is also greater than that communicated thereto during the burning of the charge 90, but is preferably less than that which would otherwise be generated by the charge 90.

i-Means is provided for suspending the apparatus shown inFigure 1 within the casing of a well bore and for selectively igniting the powder charges 40 and 90. Such r means comprises a selective firing head 134, such as indicated at 29 in Figure 10 of US. Patent No. 2,756,677

with element 23 removed, secured to the upper end of the driving head 10. A support cable 136 is secured to the firing head 134 whereby the apparatus shown in Fig ure 1 can be raised and lowered within the casing in a -borehole. Each of the heads 10, 12, 14, and 16 has an individual electric cable incorporating a pair of electrical conductors extending vertically therethrough. In the case of the driving head 10, the electric cable isjdesignated by the numeral 138 and includes insulated electrical conductors 140 and 142 and extends through the head 10, as indicated in dashed outline at 144 and 146. In the case of the working head 14, an electric cable 138 extends therethrough, as indicated in dash'ed outline. at 150, while the similar electric cable extends extending through the heads 10, 12, 14, and 16 are flex ible so as to facilitate expeditious coupling and uncoupling of the individual electric cables when coupling or uncoupling heads 10, 12, 14, and 16. The cable 154 of the retracting head 12 extends below the head 12 and is detachably coupled by a liquid-tight coupling member 164 to the lower end of the electric cable 82 that extends through the plug 74, whereby the cables 82 and 154 can be detached when it is desired to remove the plug 74.

Thus, it will be seen that with the electric cables thus far described, coupled as shown, the delivery of an electrical current through the conductors 1-40 and 142 of the cable 138 will energize and cause the igniter 84 to operate and ignite the powder charge 90.

A further electric cable 166 including insulated electrical conductors 168 and 170 is provided, the lower end I of which is detachably coupled to the upper end of the electric cable 32 in the plug 24 by a coupling member 172, whereby the igniter 34 can be caused to ignite the powder charge 40 upon the passage of an electric current through the conductors 168 and 170.

It will be understood that the electric cables 138 and 166 are coextensive upwardly from the apparatus shown in Figure 1 with thesupporting cable 136, whereby the operation of the igniters 34 and 84 can be controlled from the earths surface when the apparatus shown in Figure l is lowered in a casing in a borehole by means of the supporting cable 136. Preferably, the supporting cable 136 is of a composite type so as to incorporate the electrical conductors 140, 142, 168, and17ii therein, so that only a single composite cable must be manipulated in raising and lowering the apparatus shown in Figure 1 within the casing in a borehole.

From the foregoing, the operation of the illustrated embodiment of the invention will be readily understood. The apparatus is assembled, as shown in Figure 1, with the same loaded with the powder charges 40 and 90 and the same filled with a hydraulic liquid and air, as previously described. Inasmuch as the work etfort to be exerted by the driving head 10 normally will exceed that to be exerted by the retracting head 12, the powder charge 40 is larger than the powder charge 90', as shown in Figure 1. It will be appreciated that a greater or lesser number of working heads may be asesmbled in the apparatus than the two shown in Figure 1, it being only essential that the hydraulic conduits and electric cables be coupled in a manner in accordance with that illustrated in connection with the working heads 14 and 16 in Figure 1, and that chambers 22 and 71 be sized to contain sufficient hydraulic liquid to extend and retract working heads 66.

With the apparatus assembled as shown in Figure 1,

the same is lowered within the casing in a borehole to a position where it is desired that the casing be deformed and perforated, such as for the purpose of producing fractures in a concrete sheath surrounding the casing and for producing perforations in the casing communicating with such fractures. With the apparatus shown in Figure 1' so positioned, an electric current is passed through the electric conductors 168 and 1711, thereby causing the igniter 34 to ignite the powder charge 40, with the result that the work engaging members of all the working heads corresponding to the work engaging member 66 through the working head 16, as indicated in dashed out line at 15 2. In the case of the retracting head '12, the

of the working head 14 are projected outwardly from the working heads with considerable force to an extent limited by engagement of the piston 60 with the gland 54- and discs 30 are ruptured to permit the working heads 66 to be retracted. Such projecting of the work engaging members from the working heads results in the work engaging member forcibly engaging one side of the casing, while the convex portion of the cylinder head in the opposite end of the working head forcibly engages the opposite side of the casing.

As shown clearly in Figure 2, the work engaging member 66 has a generally hemispherical outer end configuration, as shown at 174, that has a superimposed, substantially smaller conical tip 176 thereon. The illustrated configuration of the Work engaging member 66 is such that the conical tip pierces or punctures the casing upon the work engaging member 66 being projected from the head 14, with such piercing or puncturing of the casing being followed by the convex portion 174 bulging or deforming the casing outwardly around the puncture or perforation by the conical tip 176. Reaction to the force of the work engaging member 66 engaging the casing results in the convex surface 50 of the cylinder head 46 being forced against the side of the casing opposite the work engaging member 66 to such an extent that the casing is bulged outwardly thereby. It is within the scope of the present invention that, if desired, a perforating point can be positioned on the convex surface 50 whereby a further puncture of the casing can be effected accompanied by an outward bulging of the casing, or that appropriately shaped heads be substituted for engaging member 66 to etfectother types of perforations such as ones which penetrate through pipe and cement directly to the formation.

After the powder charge 40 has been ignited so as to cause the working heads to puncture and bulge the easing, an electric current is passed through the electrical conductors 140 and 142 so as to cause the igniter 84 to ignite the powder charge 90 with the result that the work engaging members of all of the working heads are hydraulically forced into the retracted positions within their respective working heads and when they abut cylinder heads 46, discs 80 will rupture to releast the system pressure to the well bore. Such retraction of the work engaging members into their respective heads frees them from engagement with the casing and the perforations produced therein so that the apparatus can be Withdrawn from the casing by means of the supporting cable 136.

After the apparatus has been withdrawn from the casing, the plugs 24 and 74 can be removed from the heads and 12, respectively, and the powder charges 40 and 90 as well as the igniters 34 and 84 replaced for reuse of the apparatus. Provision of the blowout discs 30 and 80 in the heads 10 and 12 also affords a safety factor for preventing destruction of any components of the apparatus in the event that the pressures generated within the system by the ignition of the powder charges becomes excessively high for any reason.

Although the illustrated and described embodiment of the invention emphasizes the freedom of choice of the number of working units to be employed as well as the flexibility between the various units, it is to be understood that it is Within the scope of the invention that such choice and such flexibility can be dispensed with upon constructing all the driving and working heads .as an essentially monolithic composite structure. Flexibility is of course a valuable feature where a substantial vertical extent of working heads are employed and where the borehole is crooked, as sticking or jamming can be avoided.

It is also within the province of the invention that the couplings connecting the fluid conduits intermediate the heads can be eliminated. This can be accomplished, for example, by forming the conduits 98, 100, 104, 106, and 110 as a single continuous piece of tubing extending between the heads 10 and 12 through the working heads 14 and 16. The tubing is preferably flexible and is assembled with the heads after the latter have been assembled. The tubing is perforated at spaced positions so as to communicate fluid pressure to the pistons 60, with the passageways 92 being provided with sealing rings to prevent leakage of fluid. Similar considerations apply to the conduits 1.16. 120, 122, 130, and 126, as Well as to the electrical conduits extending through the working heads.

The illustrated preferred embodiment of the invention has been described in substantial detail for the purpose of conveying a full and complete understanding thereof, and an inference of narrowncss of inventive scope is not to be drawn from such detailed description. The actual scope of the invention must be obtained upon reference to the appended claims.

I claim:

1. Hydraulic apparatus comprising driving and retracting heads; each of said heads comprising a housing defining a closed cylindrical chamber having first and second ends and having an opening therein closed with pressure relief means, a piston in said chambers, said chambers being adapted to contain a charge intermediate the first end thereof and the piston; a working head comprising a housing defining a closed cylindrical chamber having first and second ends, the first end of which is provided with an opening therethrough of lesser transverse cross section than that of the chamber, a piston in said chamber within said working head, a cylindrical projection secured to the piston, said projection slidably and sealingly extending into said opening when the piston is positioned adjacent the second end of the chamber, work engaging means carried by the end of the projection remote from the piston; means affording fluid communication between the first end of the chamber of the working head and the second end of the chamber of the retracting head, means affording fluid communication between the second end of the chamber of the working head and the second end of the chamber of the driving head; said last two named means, the portions of the chambers of the driving and retracting heads intermediate their second ends and the pistons therein, and the chamber of the working head being adapted to confine a fluid working medium that is separated into two distinct portions by the piston in the working head; and means for selectively igniting the charges in the driving and retracting heads.

2. Hydraulic apparatus comprising driving and retracting heads; each of said heads comprising a housing defining a closed cylindrical chamber having first and second ends and having an opening therein closed with pressure relief means, a piston in said chambers, said chambers being adapted to contain a charge intermediate the first end thereof and the piston; a plurality of working heads each of which comprises a housing defining a closed cylindrical chamber having first and second ends, the first end of which is provided with an opening therethrough of lesser transverse cross section than that of the chamber, a piston in said chamber within said working head, a cylindrical projection secured to the piston, said projection slidably and sealingly extending into said opening when the piston is positioned adjacent the second end of the chamber, work engaging means carried by the end of the projection remote from the piston; means affording fluid communication between the first ends of all the chambers of the working heads and the second end of the chamber of the retracting head, means affording fluid communication between the second ends of all the chambers of the working heads and the second end of the chamber of the driving head; said last two named means, the portions of the chambers of the driving and the retracting heads intermediate their second ends and the pistons therein, and the chambers of the working heads being adapted to confine a fluid working medium that is separated into two distinct portions by the pistons in the working heads; and means for selectively igniting the charges in the driving and retracting heads.

3. A tool adapted to be raised and lowered within a well casing comprising vertically spaced driving and retracting heads and a working head disposed therebetween;

means securing all of said heads in assembled relation and means secured to the uppermost of said heads for suspending all of the heads within a well casing; said driving and retracting heads each comprising a housing defining a closed cylindrical chamber having first and second ends and having an opening therein closed with pressure relief means, a piston in said chambers, said chambers being adapted to contain a charge intermediate the first end thereof and the piston; said working head comprising a housing defining a closed cylindrical chamber having first and second ends, the first end of which is provided with an opening therethrough of lesser transverse cross section than that of .the chamber,a horizontally reciprocable piston in said chamber Within said working head, a horizontally extending cylindrical projection secured'to the piston, said projection slidably and sealingly extending into said opening when the piston is positioned adjacent the second end of the chamber, well casing engaging means carried by the end of the projection remote from the piston; means affording fluid communication between the first end of the chamber of the working head and the second end of the chamber of the retracting head, means affording fluid communication between the second end of the chamber of the working head and the second end of the chamber of the driving head; said last two named means, the portions of the chambers of the driving and retracting heads intermediate their second ends and the pistons therein, and the chamber of the working head being adapted to confine a fluid working medium that is separated into two distinct portions by the piston in the working head; and means for selectively igniting the charges in the driving and retracting heads.

4. A tool adapted tov be raised and lowered within a well casing comprising vertically spaced driving and retracting heads, and a plurality of working heads vertically stacked therebetween; means securing all of said heads in assembled relation and means secured to the uppermost of said heads for suspending all of the heads within a well casing; said driving and retracting heads each comprising a housing defining a closed cylindrical chamber having first and second ends and having an opening therein closed with pressure relief means, a piston in said chambers, said chambers being adapted to contain a charge intermediate the first end thereof and the pistomeach of said working heads comprising a housing defining a closed cylindrical chamber having first and second ends, the first end of which is provided with an opening therethrough of lesser transverse cross section than that of the chamber, a horizontally reciprocable piston in said chamber within said working head, a horizontally extending cylindrical projection secured to the piston, said projection slidably and sealingly extending into said opening when the piston is positioned adjacent the second end of the chamber, well casing engaging means carried by the end of the projection remotefrom the piston; means'affording fluid communication'between the first ends of all the chambers of the working heads and the second-end of the chamber of the retracting head, means affording fluid communica tion between the second ends of all the chambers of the working heads and the second end of the chamber ofthe driving head; said last two namedrneans, the portions of the chambers of the driving and the retracting heads intermediate their second ends and the pistons therein, and

securing the heads in assembled relation is comprised of one of each adjacent pair of heads being provided with a groove in which a tongue carried by the other of such pair of heads is detachably engaged to prevent vertical separation, and wherein each of said communication affording mens extends between each adjacent pair of working heads with such extending portions of such means being comprised of a conduit provided with a releasable coupling.

6. The combination of claim 4, wherein each head is detachably secured to each head immediately adjacent thereto, and wherein each of said communication affording means extends between each adjacent pair of working heads with such extending portions of such means being comprised of -a conduit provided with a releasable coupling.

7. A hydraulically actuated working head comprising a housing having a horizontal cylindrical opening therethrough, a cylinder head threadingly secured to the housing and closing one end of the opening, said cylinder head having a convex surface projecting outwardly from the housing for engaging a casing and deforming the latter on being forced thereagainst, a gland threadingly engaging the housing and closing the other end of the opening, said gland having a cylindrical opening therethrough of lesser diameter than the opening through the housing, a piston slidably and sealingly fitted in the opening for horizontal reciprocation, a casing engaging member slidably and sealingly fitted in the opening 7 through the gland for horizontal reciprocation, said member being secured to the piston and having a length such that the same reciprocates between positions projecting from and retracted within the gland during reciprocation of the piston, a first passageway in the housing communicating with the opening in the housing intermediate the piston and the cylinder head, and a second passageway in the housing communicating with the opening in the housing intermediate the piston and the gland.

8. A hydraulically actuated working head comprising a housing having a horizontal cylindrical opening therethrough, a cylinder head threadingly secured to the housing and closing one end of the opening, said cylinder head having a convex surface projecting outwardly from the housing for engaging a casing and deforming the latter on being forced thereagainst, a gland threadingly engaging the housing and closing the other end of the. opening, said gland having a cylindrical opening therethrough of lesser diameter than the opening through the housing, a piston slidably and sealingly fitted in the opening for horizontal reciprocation, a casing engaging member slidably and sealingly fitted in the opening through the gland for horizontal reciprocation, said member being threadingly and detachably secured to the piston and having a length such that the same reciprocates between positions projecting from and retracted within the gland during reciprocation of the piston, a first passageway in 1 the housing communicating with the opening in the housing intermediate the piston and the cylinder head, :a second'passageway in the housing communicating with the opening in the housing intermediate the ,piston and the gland, and means on the top of and on the bottom of thehousing for detachably securing'the same to additional working heads disposed above and below.

the chambers of the working heads beingadapted to. confine a fluid working medium that is separated into two distinct portions by the pistons in the working heads; and 1 means forselectively igniting the charges in the driving and retracting heads. 1

5. The combination of claim 4, wherein the means References Cited in the file of this patent j UNITED STATES PATENTS 2,066,409 Loring et a1. Ian. 5, 1937 2,530,805 Bond Nov. 21, 1950 2,687,776 Baker Aug.'31, 1954 2,692,023 Conrad Oct. 19,1954

12,695,065; 1 Baker et al. Nov. 23, 1954 

